Internal combustion engines for operation of vehicles, such as automobiles and trucks, utilize a wide variety of accessory components. Many of the components, such as water pumps, have pulleys which are driven by a belt attached to the crankshaft of the engine and thus operate at some percentage of engine speed. Other components also have pulleys driven by a serpentine belt, such as air conditioning, compression generators, and the like.
Efforts are being made today to reduce the power consumption of engine accessories in order to improve fuel economy and reduce emissions. At the same time, the accessories need to have improved operation and durability. It also would be preferable if such accessories, such as water pumps, could be made to operate at variable speeds or with less power in order to reduce the load on the engine and, in turn, improve fuel economy and reduce undesirable emissions from the engine.